Mostly two-stroke engines are used as a drive in motor-driven chain saws, cutoff machines, brushcutters or the like. Disadvantages are associated with theses engines which result from the mode of operation thereof. Even though the technical development has made significant advances, the exhaust-gas quality of a two-stroke engine can hardly be increased because of the port control.
It is known to provide inlet and outlet valves in two-stroke engines and to actuate these valves via a suitable cam drive and a corresponding valve control. Especially for portable handheld work apparatus, problems result with respect to the necessary lubrication of the cam drive and the valve control because the internal combustion engine must be operationally reliable independent of position. For this reason, a rotation lubrication is therefore hardly suitable and is not justified because of the great complexity. It is especially important with portable handheld work apparatus that technical improvement should not lead to excessive weight because this would limit the use of the apparatus.